The effect of changes in organic carbon input from aboveground litter and belowground roots on soil active nitrogen content is currently a topical issue in academia. However, it is unclear about the influence of organic carbon input methods on soil active nitrogen content during the freeze-thaw season. The root-only organic carbon input treatment (litter removal) and the litter-only organic carbon input treatment (root removal) were measured, the root and litter retention treatment was a control group. This study investigated the dynamics of soil microbial and mineral nitrogen content. The results show that: (1) the mode of organic carbon input has a significant effect on the soil active nitrogen content. Soil microbial biomass nitrogen content in the root-only organic carbon input method and total mineral nitrogen in the root-only organic carbon input method are 10.5% and 12.3% higher than those in the control treatment, respectively. (2)The duration of input changes the effect of the organic carbon input method on the soil active nitrogen content: the long-term root-only and litter-only organic carbon input treatments decrease the soil microbial biomass nitrogen content, and the response rates are 0.451 and 0.422, respectively. (3) The seasonal difference is a key factor influencing the effect of organic carbon input methods on soil active nitrogen content: the litter removal during the freeze-thaw season increases the total mineral nitrogen content, while litter removal during the growing season decreases the total mineral nitrogen content, and the response rates are 0.404 and 0.121, respectively. The results highlight the importance and regulation of organic carbon inputs on soil active nitrogen content, which varies with the season and the input duration of the treatment.